Electric translating circuits



.March 21, 1933.

A. H. MITTAG 1,902,460

ELECTRIC TRANSLATING CIRCUITS Filed Sept. 14, 1952 2 sheet s 'sheet 1 Inventor: Albert H. Mittag,

March 21, 1933. M T 1,902,460

ELECTRIC TRANSLATING CIRCUITS Filed Sept. 14. 1932 2 Sheets-Sheet 2 Inventor: Albert H. Mittag,

y His Attorney.

Patented Mar. 21, 1933 umrso STATES ALBERT H. MI'rTAe,"

PATENT o F'icE i OF SGHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIG TRANSLATING CIRGUITS Application filed September 14, 1932. Serial'lN'o. 634,001.

My invention relates to electric translating circuits and more particularly to such circuits in which a plurality of vapor electric valves are operated in parallel.

In many. electric translating circuits and electric valve converting apparatus such, for example, as those for transmitting energy between direct and alternating current circuits, direct current circuits of different voltages or alternating current circuits of the same or different frequencies, the use of vapor electric discharge valves has been found particularly advantageous because of the relatively large amounts of power which may be handled at ordinary operating voltages. When handling a considerable amount of power, it sometimes becomes desirable to operate two or more vapor electric discharge valves in parallel and in such cases there arises the problem of maintaining a distribution of the current between the several par allel connected electric valves in accordance with their ratings, or, as is usually the case, maintaining an equal division of current between the valves. Where the valves conduct periodically, as is usually the case, the principal condition that must be satisfied is that all of the valves shall start conducting simultaneously. Heretofore, it has been proposed to include an impedance device directly in series with the anode-cathode circuit of each of the valves, the natural regulation characteristics of these impedance devices tending to force an equal distribution of current between the valves. However, when one of the parallel connected'valves begins to conduct current, the terminal voltages across the other valves are substantially reduced and this method does notatford a completely satisfactory solution of the problem.

It is an object of my invention, therefore, to provide an improved electric translating circuit including a plurality of vapor'electrio valves operating in parallel which will overcome the above mentioned disadvantages of the arrangements of the prior art and which will be simple and reliable inoperation.

It is another object of my invention to provide an improved electric translating circuit including plurality of vapor electric valves operating in parallel which will insure a distribution of the current between the parallel connected valves in accordance with their ratings. 7

It is a further object of my invention to provide an improved electric translating circuit including a plurality of vapor electric valves operating in parallel which will equalize the current flowing in the parallel connected valves.

In accordance with my invention, a group of parallel connected vapor electric valves in an electric translating circuit are'provided with control grids, and the grids are excitedto render the electric valves normally simultaneously conductive. In order to prevent the startmg of current in one of the valves and the-consequent reduction in the terminal voltage across the other valve-s from so affecting the other valves that they will be prevented from starting, there is included means responsive to .the current in each valve for modifying the action of the grid circuits ofthe other valves rapidly to start the current in these nonconducting valves. For example, an inductive winding may be included in the anode-cathode circuit of each of the electric valves, and this winding, or an auxiliary inductive. winding coupled thereto, may modify the action of the grid circuits of the other valves so that upon the initiation of current in one valve, positive impulses are impressed upon the grids of the nonconducting valves torender them conducting.

For a better understanding of my invention, together with other. and further objects I Fig. 2 shows a modification of the grid control circuit of the arrangement ofFig. 1;. Fig. 3 illustrates a modification of the ar v rangement of Fig. 1 to adapt the arrangement to the use of amultiple anode, single cathode, grid controlled mercury arc rectier, while Figs. 41 and 5 represent modified arrangements of the reactance devices illustrated in Fig. 3. I

Referring now more particularly to Fig. 1 of the drawings, there is illustrated an arrangement for transmit-ting energy between an alternating current circuit 10 and a direct current circuit 11. For thepracticing of my invention it is immaterial whether the appa ratus is operating as a rectifier, transmitting energy from the alternating current circuit 10 to the direct current circuit 11, or as an inverter, transmitting energy in the opposite direction. This apparatus includes a transformer 12 provided with a winding 13 connected to the circuit 10 and a winding 14 provided with an electrical midpoint connected to one side of the direct current circuit 11 and with end terminals connected to the other side of the direct current circuit 11 through the groups of electric valves 15, 16 and 17, and 18, 19 and 20, respectively. Each of the valves 1520,inc., is provided with an anode, a cathode and a control grid and is of the vapor electric discharge type in which the starting of current in a valve is determined by the potential on its control grid, but in which the current flowing in a valve can be interrupted only by reducing its anode potential below the critical value. Between the cathodes of electric valves 1520, 'inc., and the lower side of the direct current circuit 11, are connected inductive windings 21-26, inc., respectively. In order to control the energy transmitted between the circuits 10 and 11, the grids of the several valves 15-20, inc., are connected to their respective cathodes through current limiting resistors 27, opposite halves of the secondary winding of a grid transformer 28, andthe several inductive windings 21-26, inc. The primary winding of the grid transformer 28 maybe energized from any suitable source of alternating current of the desired frequency, or, in case the circuit 10 is energized with an independent source of electromotive force as when the apparatus is operating as a rectiher, the primary winding of the transformer 28 may be energized therefrom through a rotary phase shifting transformer 29 and a phase splitting circuit 30, an arrangement well known in the art.

The general principles of operation of the above described apparatus when operating as either a rectifier or an inverter, will be well understood by those skilled in the art. While I do not wish to be limited thereto, I believe that the most probable explanation of the manner in which the apparatus functions to maintain the correct distribution of currentbetween the several parallel connected electric valves, is as follows: Assume for example, that the apparatus is operating as a rectifier and thatthe left hand terminal of the winding 14 is positive so that current will tend to flow through the electric valves 15, 16 and 17. When the potential supplied to the grid transformer 28 makes the grids of the valves 15, 16 and 17 positive, tending to render them conductive simultaneously, current will tend to flow in one or more of these valves. If it be assumed that electric valve 15, for example, begins toconduct current before the valves 16 and 17, the potential across the valves 16 and 17 will drop considerably. At the same time, however, a large portion of the supply voltage will momentarily appear across the reactance device 21 and this voltage will be impressed upon the grid of the valve 16' through the circuit includin the grid-cathode circuit of the valve 15, which is conductive,-the two current limiting resistors 27- interconnecting the grids of the valves 15 and16, the grid-cathode circuit' of the valve 16 and the inductive winding 22. Through a sinlilar circuit,'this same voltage will be impressed between-the grid and cathode of the valve 17 In other words, as soon as one of the parallel connected valves begins to conduct current, the voltage across the reactance device in series therewith impresses a positive impulse upon the grids of the non-conductive valves and this impulse occurs substantially instantaneously while a large portion of the voltage across the series connected inductive windings still obtains and before the terminal voltage across the nonconductive valves has dropped'substantially. These positive impulses of grid potential on the nonconductive valves insures that they fire or become conductive almost instantaneously. It has been found that by thus insuring that all parallel connected valves become conductive simultaneously, only a 4 very slight amount of reactance need be included in the inductive windings in series with the several valves to insure substantial equalization of the current between the parallel connected valves, or distribution of the current in accordance with'the'ir ratings. While I have illustrated my invention as applied to an arrangement in which three electric valves are operated in parallel it will be'obvious to thoseskilled in the art that it is equally applicable toarrangements including any number of parallel connected valves;

The arrangement of Fig. 2 is similar to that of Fig. 1 with the exception that the grid resistors 27 are included in the cathode con-- nection to the grid transformer rather than in the grid connection, as in the arrangement of Fig. 1. In this arrangement, the grids of the several electric valves are directly connected together. With such an arrangement the grid resistors are not included in the circuit by means of which the reactance devices 21-26, inc., impress their transient potentials upon the grids of the nonconductive electric valves. F or example, when the valve 15 becomes conductive, so that its grid is connected to its cathode through the ionized vapor, the voltage of the inductive winding 21 will be impressed directly between the grid and cathode of the valve 16, for example, through the grid-cathode circuit of the valve 15, the grid-cathode circuit of the valve 16 and the inductive winding 22. In this figure the grid transformer 28 is illustrated as being provided with two independent secondary windings which are connected to excite the grids of thevalves 15, 16 and 17 and 18, 19 and 20, respectively. If desired, the two inside terminals of these windings may be connected di- 5 rectly together to form an electrical midpoint,

as in the arrangement of Fig. 1. With such a connection, the deionizing current of the electric valves may flow directly fromthe secondary winding of the grid transformer 28 20 through the grid-cathode circuits of the'two groups of valves and the inductive windings 21-26, inc., without flowing through the grid resistors 27. Such an arrangement may be of advantage'when the apparatus is operat 25 ing as an inverter, transmitting energy from the circuit 11 to the circuit 10.

In Fig. 3 there is shown a modification of the arrangement of Fig. 1 suitable for employing a plurality of electric valves or valve such for example, as is the case when employing a multiple-anode, grid controlled mercury arc rectifier. In this arrangement the end terminals of the winding 14 of the transformer 12 are connected to the lower side of the direct current circuit 11 through the anodes 3237, inc., of the mercury arc rectifier 31. Included in the connections to the several anodes 32-37, inc., are inductive these auxiliary inductive windings are con nectcd directly to the grids associated with the corresponding anodes 32-37, inc., while their other terminals are connected together to form a neutral.

The operation of this apparatus is similar to that described above in connection with Figs. 1 and 2. If one of theparallel connected anodes 32, 33 and 34, for example, the anode 32, should become conductive first, the current building up in the inductive winding 38 will induce a voltage in the auxiliary winding 44 which will impress a potential upon the grid associated with the anode 33 through the auxiliary winding 45 and the two cur rent limiting resistors 27 interconnecting. the grids of these two anodes. Similarly, it .will simultaneously impress a positive potential 65 upon the grid associated with the anode 34 to paths having a single cathode potential,

In the arrangementofFig. 4 the windings 38, 39 and 40 and their associated auxiliary windings 44, 45 and '46 are wound on three separate legs of a three-legged magneticvcore member 50. The connections are such that when current is flowing simultaneously 1n the windings 38, 39 and 40, the magnetomo- 'tive forcesof these windings buck each other with the result that no flux flows in the core member 50. and no voltage isinduced in the auxiliary windings 44, 45 and 46. Should on'ey'or more of the windings 38, 39 and 40 be deenergized, however, due to the failure of its associated electric valve to become cond uctive, a flux will be set up in thecorresponding portion of the magnetic circuit and the voltage induced in the associated auxiliary winding will impress a positive impulse uponthe grid of the valve which is nonconductive. If desired, serially connected ter tiary windings'51, 52 and 53 maybe mounted on'the several legs of the core'member 51 to improve the magnetic coupling betweenthe severalactivewindings. i

In'the modification shown inFig. 5,the several main'windings 38, 39 and 40 and the auxiliary windings'44, 45fand 46, are each divided into two portions and wound on two separate legs of the magnetic core structure 50, as illustrated, in order to improve the magnetic interlinkage between the several coils. In'other respects, the operatl similar to that described above.

WhileIhave described what Iat present consider the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made withoutdeparting from my invention, and I, therefore, aim in the appended claims to cover all such changes and' modifications as, fall within the true spirit and scope of my invention. a Y fWhat I claim as new and desire to secure by Letters Patent of the United States is 1. In an electric translating circuit, apair n is of grid controlled vapor electric valves connectcd in parallel, a grid circuit'for each of said valves, and means for' forcing a distribu-" t1on of the current between said valves in accordance with their ratings comprising means responsive to the current in each valve connected in parallel, a grid circuit for each of said valves, and means for equalizing the current in said parallel connected valves comprising meansresponsive to the current in each valve. for modifying the action. of the grid circuits of the other valves.

'- 3. In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallel, agrid circuit foreach of said valves, means for exciting said grid circuits normally to render said valves conductive simultaneously, and means responsive to the starting of current in one of said valves for imparting an impulse to the grid circuits of the other valves'to initiate a current therein. 1

4:. In an electric translating circuit,- a plurality of grid controlled vapor electric valves connected in parallel, agrid circuit for each of said valves, means 'for exciting said grid circuits normally to render saidrvalves conductive simultaneously, and an inductive winding, included in the anode-cathode circuit of each of said valves and connected in circuit with the grids of the other valves to impress a positive impulse upon the grids of any of said other valves'which are nonconductive upon the initiation of current in its associated valve.

5. In an electric translating circuit, a plurality of grid controlled vapor electric valves connectedin paralleha grid circuit for each of said valves, means for exciting said'grid circuits normally to render said valves con.- ductive simultaneously, and an inductive winding included in the anode-cathode circuit'of each of said valves and connected in the grid circuits of the other valves through the grid-cathode circuit of its associated valve, whereby the initiation of current in any valve is effective to impress the full voltage of said winding upon the grids of the nonconductivevalves. v

6. In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallehan inductive winding for each of said valves, the cathodes of said valves being connected together through said windings, a grid circuit for each of said valves, and means for exciting said grid circuits normally to render said valves conductive simultaneously, the grid circuit of each valveincluding also the inductive windings of the other valves, each connected in series with the grid-cathode circuit of its associated valve.

- 7. In an electric translating circuit, plurality of grid controlled vapor electric valves connected in parallel, an inductive winding for each of said valves, the cathodes of said valves being connected together through said inductive windings, a grid circuit for each of said valves, said gridcircuits having a common connection connected to the common connection of said inductive windings.

8. In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallel, an inductive winding for each of said valves, the cathodesof said valves being connected together through said inductive windings, a gridcircuit for each of said valves including acurr'ent limiting resistor, and means for exciting said grids normally to render said valves conductive simultaneously, one terminal of said exciting means being connected directly 'to the several valve grids, and the other being connected to the cathode of each valve through its associated grid resistor. a

9. In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallel, a. grid circuit for each of said valves, means for exciting said grid circuits normally to render said valves conductive simultaneously, an inductive winding includedv in the anode-cathode circuit of each of said valves, and an auxiliary inductive winding coupled to each of said first mentioned windings and connected in circuit with the gridof its corresponding valve, said aux iliary windings being effective upon the initiation of current in any of said valves to impress positive impulses on the grids of the nonconductive valves.

10. .In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallel, a grid circuit for each of said valves, means for exciting said grid circuits normally to render said valves conductive simultaneously, an inductive winding included in series with the anode of each valve, and an auxiliary inductive winding coupled to each of said first mentioned windings. one terminal of each of said auxiliary windings being connected to the grid of the corresponding valve, and the other terminals of said inductive winding being connected together.

11. In an electric tra slating circuit, a plurality ofgrid controlled vapor electric valves connected in parallel. a grid circuit for each of said valves, means for exciting said grid circuits normally to render said valves conductive simultaneously, a reactance device comprising a multi-legged core member and an inductive winding mountedon each leg of said core, nected in the anode-cathode circuit of each of said valves,'and an auxiliary inductive winding coupled to each of said first mention'ed windings and connected in circuit with the grid of its corresponding valve, said auxiliary windings being effective upon the initiation of current in any of said valves to impress positive impulses on the grids of the nonconductive valves. 7

12. In an electric translating circuit, a plurality of grid controlled vapor electric valves connected in parallel. a grid circuit for each of'said valves, means for exciting said grid circuits'normally to render said valves conductive simultaneously, a reactance device comprising a multi-legged core member and an inductive winding mounted on each leg of saidvcore, one of said windings being connected in the anode-cathode circuit of each one of said windings being conof said valves, an auxiliary inductive winding coupled to each of said firstmentioned windings and connected in circuit with the grid of its corresponding valve, and an auxiliary Winding system forsaid reactance device to improve the coupling between the several valve circuits. h In Witness whereof I have hereunto set my and.

ALBERT H. MITTAG.

DISCLAIMER 1,902,460.Albert H. Mittag, Schenectady, N. Y. ELECTRIC TRANSLATING CIR- CUITS. Patent dated March 21, 1933. Disclaimer filed December 8, 1937,

by the assignee, General Electric Company. Hereby enters this disclaimer to claim 11in said specification.

[Ofiiaial Gazette January 4, 1.938.] 

